In general, a scroll compressor includes a scroll wrap, and performs a compression operation through a relative movement between a fixed scroll fixed irrespective of a rotation of a drive shaft and a swivel scroll configured to swivel according to a rotation of the drive shaft. There are circulated many type of scroll compressors in the market.
An example of such a scroll compressor is disclosed in Korean Laid-Open Patent No. 1998-0050613, and will be briefly described with reference to FIG. 1A and FIG. 1B.
As shown in FIG. 1A and FIG. 1B, according to the conventional scroll compressor, upper and lower frames 2 and 3 are installed inside a sealed vessel 1 at upper and lower portions of the sealed vessel 1, a stator 4 is fixed and installed between the upper and lower frames 2 and 3, a rotor 5 is inserted into and installed in an inner periphery of the stator 4, a drive shaft 6 is press-fitted into a central portion of the stator 5 such that it passes through a central portion of the upper frame 2, and a swivel scroll 7 having an involute wrap 7a is eccentrically coupled to the drive shaft 6 and is positioned on an upper end surface of the upper frame 2.
A fixed scroll 8 engaged with the wrap of the swivel scroll 7 to from a compression chamber is positioned on the upper side of the swivel scroll 7 and engaged with the periphery of the upper frame 2, and an Oldham ring 9 serving as a rotation preventing mechanism is coupled between the upper frame 2 and the swivel scroll 7.
The reference numeral 10 represents a discharge cover, 11, a check valve housing, 12, a suction pipe, and 13, a discharge pipe.
In the conventional scroll compressor, the rotor 5 is rotated inside the stator 4 when electric power is applied to it to rotate the drive shaft 6, in which case the drive shaft eccentrically rotates the swivel scroll 7 by an eccentric distance. Then, the swivel scroll 7 is swiveled by the Oldham ring 9 about the center of the shaft thereof at a distance separated by a swivel radius.
A compression chamber (pocket) is formed between the wraps 7a and 8a of the swivel scroll 7 and the fixed scroll 8 by the swivel movement of the swivel scroll 7 such that it is moved to the center thereof by the continuous swivel movement, whereby its volume is reduced and the suctioned refrigerant gas is further compressed.
Here, the rear surface of the fixed scroll 8 and the bottom surface of the discharge cover 10 are recessed and protruded once respectively such that a back pressure chamber 14 is formed on the corresponding surface of the recess and protrusion, a back pressure hole 14a communicated with the compression chamber of the fixed scroll 8 is formed on one side of the back pressure chamber 14, and sealing members (not shown) are interposed at opposite sides of the back pressure chamber 14.
According to the conventional scroll compressor, a refrigerant gas introduced through a suction opening (not shown) formed in the fixed scroll 8 is suctioned at opposite ends of the circumference of the scroll as the swivel scroll 7 swivels and is confined in two crescent moon-shaped pockets (compressions) having the same volume. The volume of the pockets is continuously reduced to compress the refrigerant gas in the process of moving the center thereof.
In the conventional scroll compressor, the back pressure hole 14a communicated with the back pressure chamber 14 is formed at a predetermined position of the fixed scroll 8, and a refrigerant gas of an intermediate pressure enters the back pressure chamber 14 through the back pressure hole 14a such that the pressure of the refrigerant gas attaches the fixed scroll toward the swivel scroll 7, making it possible to prevent leakage of the refrigerant gas.
However, since the conventional scroll compressor has a structure adapted to axially move the fixed scroll with respect to the swivel scroll 7, its structure is unstable and vibrations are severe.
Moreover, when the swivel scroll 7 is pushed downward by the high pressure of the pocket, it contacts an upper end surface of the upper frame 2. Accordingly, excessive friction is caused between the swivel scroll 7 and the upper frame 2, deteriorating the efficiency of the compressor and causing damage.